Recently Adopted and Recently Issued Accounting Standards (Policies)	12 Months Ended
Dec. 31, 2014
Accounting Policies [Abstract]
Adoption of New Accounting Standards	Recently Adopted and Recently Issued Accounting Standards: Adopted: Effective January 1, 2014, Ambac adopted ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The ASU requires an entity to present an unrecognized tax benefit in the financial statements as a reduction to a deferred tax asset for an NOL carryforward, a similar tax loss, or a tax credit carryforward except when: i) an NOL carryforward, a similar tax loss, or a tax credit carryforward is not available as of the reporting date under the governing tax law to settle taxes that would result from the disallowance of the tax position and ii) the entity does not intend to use the deferred tax asset for this purpose. If either of these conditions exists, an entity should present an unrecognized tax benefit in the financial statements as a liability and should not net the unrecognized tax benefit with a deferred tax asset. The adoption of this ASU did not have a material effect on Ambac’s financial statements. Issued: In April 2014, the FASB issued ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360) - Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. The objective of this ASU is to limit discontinued operations reporting to disposals of components of an entity that represent strategic shifts that have (or will have) a major effect on an entity's operations and financial results. Under current U.S. GAAP, many disposals, some of which may be routine in nature and not a change in an entity's strategy, are reported in discontinued operations. The ASU also requires certain expanded disclosures for discontinued operations and disclosure of the pre-tax profit or loss of an individually significant component of an entity that does not qualify for discontinued operations reporting. The ASU is effective prospectively for all disposal (or classifications of held for sale) components that occur within annual periods beginning on or after December 15, 2014. Ambac will adopt ASU 2014-08 on January 1, 2015. The adoption of this ASU is not expected to have a material effect on Ambac's financial statements. In June 2014, the FASB issued ASU 2014-12, Compensation - Stock Compensation (Topics 718) - Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. Generally, share-based payment awards that require a specific performance target to be met also require an employee to render service until the performance target is achieved. However, in some cases, the terms of an award may provide that the performance target could be achieved after the employee completes the requisite service period. Under current U.S. GAAP, there is no explicit guidance on how to account for share-based payment awards with performance targets that could be achieved after the requisite service period. This ASU is intended to resolve diversity in practice with respect to how the performance target is considered in the grant-date fair value of the award, which impacts the amount of compensation cost recognized over time. The ASU requires that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. As a result, the performance target would not be reflected in estimating the fair value of the award at the grant date. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted. Entities may apply this ASU either (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. Ambac presently follows the guidance in ASU 2014-12 for its share-based awards which have performance targets, thus there will be no material impact on Ambac's financial statements. In August 2014, the FASB issued ASU 2014-13, Consolidation (Topic 810): Measuring the Financial Assets and the Financial Liabilities of a Consolidated Collateralized Financing Entity. A collateralized financing entity ("CFE") is a variable interest entity with nominal or no equity that holds financial assets and issues beneficial interests in those financial assets. The beneficial interests, which are financial liabilities of the CFE, have contractual recourse only to the related assets of the CFE. Currently, a reporting entity that is required to consolidate a CFE may elect to measure the financial assets and financial liabilities of the CFE at fair value. Under the ASU, a reporting entity may elect to measure such assets and liabilities using either: i) the measurement principles in the Fair Value Measurement Topic of the ASC or ii) an alternative measurement approach specified in the ASU. The alternative measurement approach uses the more observable of either the fair value of the financial assets or financial liabilities to measure both. The ASU is intended to address diversity in practice in accounting for the measurement difference between financial assets and financial liabilities of CFEs. The ASU is effective for annual periods and interim periods with those annual periods beginning after December 15, 2015. A reporting entity may apply the ASU using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the annual period of adoption. A reporting entity may also apply the ASU retrospectively to all relevant prior periods beginning within the annual period in which ASU 2009-17, Consolidation (Topic 810): Improvements to Financial Reporting by Enterprises Involved with Variable Interest Entities, was adopted. Ambac will adopt ASU 2014-13 on January 1, 2016 and is currently evaluating the impact of the ASU on its financial statements. In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Currently, there is no guidance in U.S. GAAP about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern or to provide related footnote disclosures. The ASU requires management to assess, at each interim and annual reporting period, whether substantial doubt exists about the company’s ability to continue as a going concern within one year after the date that the financial statements are issued or available to be issued. If management determines there is substantial doubt, it should also consider whether the substantial doubt is overcome by management’s plans, and provide certain disclosures based on facts and circumstances. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2016, with early adoption permitted. Ambac will adopt ASU 2014-14 on January 1, 2017. As this is a disclosure requirement, adoption of this ASU will not have a material effect on Ambac’s financial statements. In November 2014, the FASB issued ASU 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity. The objective of this ASU is to eliminate the existing diversity in practice in accounting for hybrid financial instruments issued in the form of a share. A hybrid financial instrument consists of a “host contract” into which one or more derivative terms have been embedded. The ASU requires an entity to consider the terms and features of the entire financial instrument, including the embedded derivative features, in order to determine whether the nature of the host contract is more akin to debt or to equity. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, with early adoption permitted. A reporting entity should apply the ASU using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the annual period of adoption. Retrospective application is permitted to all relevant prior periods. Ambac will adopt ASU 2014-16 on January 1, 2016. Adoption of this ASU is not expected to have a material effect on Ambac’s financial statements. In January 2015, the FASB issued ASU 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20): Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items. Extraordinary items are defined as both unusual in nature and infrequent in occurrence. Under previous guidance, a reporting entity was required to separately present and disclose extraordinary items. This ASU eliminates from current U.S. GAAP the concept of extraordinary items. However, the ASU retains the presentation and disclosure guidance for items that are unusual in nature or occur infrequently. Items that meet either or both of these criteria must be presented as a separate component on the face of the income statement or, alternatively, disclosed in the notes to the financial statements. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply this ASU either prospectively or retrospectively to all prior periods presented in the financial statements. Early adoption is permitted provided that the ASU is applied from the beginning of the fiscal year of adoption. Ambac has not determined whether it will early adopt this ASU, however adoption of this ASU is not expected to have a material effect on Ambac’s financial statements. In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis. This ASU makes changes to the VIE model and voting interest ("VOE") model consolidation guidance. The main provisions of the ASU include the following: i) adding a requirement that limited partnerships and similar legal entities must provide partners with either substantive kick-out rights or substantive participating rights over the general partner to qualify as a VOE rather than a VIE; ii) eliminating the presumption that the general partner should consolidate a limited partnership; iii) eliminating certain conditions that need to be met when evaluating whether fees paid to a decision maker or service provider are considered a variable interest; iv) excluding certain fees paid to decision makers or service providers when evaluating which party is the primary beneficiary of a VIE; and v) revising how related parties are evaluated under the VIE guidance. Lastly, the ASU eliminates the indefinite deferral of FAS 167, which allowed reporting entities with interests in certain investment funds to follow previous guidance in FIN 46 (R). However, the ASU permanently exempts reporting entities from consolidating registered money market funds that operate in accordance with Rule 2a-7 of the Investment Company Act of 1940. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply this ASU either using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning period of adoption or retrospectively to all prior periods presented in the financial statements. Early adoption is also permitted provided that the ASU is applied from the beginning of the fiscal year of adoption. Ambac will adopt ASU 2015-02 on January 1, 2016 and is currently evaluating the impact of this ASU on its financial statements.

Recently Adopted and Recently Issued Accounting Standards:

Adopted:

Effective January 1, 2014, Ambac adopted ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The ASU requires an entity to present an unrecognized tax benefit in the financial statements as a reduction to a deferred tax asset for an NOL carryforward, a similar tax loss, or a tax credit carryforward except when: i) an NOL carryforward, a similar tax loss, or a tax credit carryforward is not available as of the reporting date under the governing tax law to settle taxes that would result from the disallowance of the tax position and ii) the entity does not intend to use the deferred tax asset for this purpose. If either of these conditions exists, an entity should present an unrecognized tax benefit in the financial statements as a liability and should not net the unrecognized tax benefit with a deferred tax asset. The adoption of this ASU did not have a material effect on Ambac’s financial statements.

Issued:

In April 2014, the FASB issued ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360) - Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. The objective of this ASU is to limit discontinued operations reporting to disposals of components of an entity that represent strategic shifts that have (or will have) a major effect on an entity's operations and financial results. Under current U.S. GAAP, many disposals, some of which may be routine in nature and not a change in an entity's strategy, are reported in discontinued operations. The ASU also requires certain expanded disclosures for discontinued operations and disclosure of the pre-tax profit or loss of an individually significant component of an entity that does not qualify for discontinued operations reporting. The ASU is effective prospectively for all disposal (or classifications of held for sale) components that occur within annual periods beginning on or after December 15, 2014. Ambac will adopt ASU 2014-08 on January 1, 2015. The adoption of this ASU is not expected to have a material effect on Ambac's financial statements.

In June 2014, the FASB issued ASU 2014-12, Compensation - Stock Compensation (Topics 718) - Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. Generally, share-based payment awards that require a specific performance target to be met also require an employee to render service until the performance target is achieved. However, in some cases, the terms of an award may provide that the performance target could be achieved after the employee completes the requisite service period. Under current U.S. GAAP, there is no explicit guidance on how to account for share-based payment awards with performance targets that could be achieved after the requisite service period. This ASU is intended to resolve diversity in practice with respect to how the performance target is considered in the grant-date fair value of the award, which impacts the amount of compensation cost recognized over time. The ASU requires that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. As a result, the performance target would not be reflected in estimating the fair value of the award at the grant date. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted. Entities may apply this ASU either (a) prospectively to all awards granted or modified after the effective date or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. Ambac presently follows the guidance in ASU 2014-12 for its share-based awards which have performance targets, thus there will be no material impact on Ambac's financial statements.

In August 2014, the FASB issued ASU 2014-13, Consolidation (Topic 810): Measuring the Financial Assets and the Financial Liabilities of a Consolidated Collateralized Financing Entity. A collateralized financing entity ("CFE") is a variable interest entity with nominal or no equity that holds financial assets and issues beneficial interests in those financial assets. The beneficial interests, which are financial liabilities of the CFE, have contractual recourse only to the related assets of the CFE. Currently, a reporting entity that is required to consolidate a CFE may elect to measure the financial assets and financial liabilities of the CFE at fair value. Under the ASU, a reporting entity may elect to measure such assets and liabilities using either: i) the measurement principles in the Fair Value Measurement Topic of the ASC or ii) an alternative measurement approach specified in the ASU. The alternative measurement approach uses the more observable of either the fair value of the financial assets or financial liabilities to measure both. The ASU is intended to address diversity in practice in accounting for the measurement difference between financial assets and financial liabilities of CFEs. The ASU is effective for annual periods and interim periods with those annual periods beginning after December 15, 2015. A reporting entity may apply the ASU using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the annual period of adoption. A reporting entity may also apply the ASU retrospectively to all relevant prior periods beginning within the annual period in which ASU 2009-17, Consolidation (Topic 810): Improvements to Financial Reporting by Enterprises Involved with Variable Interest Entities, was adopted. Ambac will adopt ASU 2014-13 on January 1, 2016 and is currently evaluating the impact of the ASU on its financial statements.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Currently, there is no guidance in U.S. GAAP about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern or to provide related footnote disclosures. The ASU requires management to assess, at each interim and annual reporting period, whether substantial doubt exists about the company’s ability to continue as a going concern within one year after the date that the financial statements are issued or available to be issued. If management determines there is substantial doubt, it should also consider whether the substantial doubt is overcome by management’s plans, and provide certain disclosures based on facts and circumstances. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2016, with early adoption permitted. Ambac will adopt ASU 2014-14 on January 1, 2017. As this is a disclosure requirement, adoption of this ASU will not have a material effect on Ambac’s financial statements.

In November 2014, the FASB issued ASU 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity. The objective of this ASU is to eliminate the existing diversity in practice in accounting for hybrid financial instruments issued in the form of a share. A hybrid financial instrument consists of a “host contract” into which one or more derivative terms have been embedded. The ASU requires an entity to consider the terms and features of the entire financial instrument, including the embedded derivative features, in order to determine whether the nature of the host contract is more akin to debt or to equity. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015, with early adoption permitted. A reporting entity should apply the ASU using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the annual period of adoption. Retrospective application is permitted to all relevant prior periods. Ambac will adopt ASU 2014-16 on January 1, 2016. Adoption of this ASU is not expected to have a material effect on Ambac’s financial statements.

In January 2015, the FASB issued ASU 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20): Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items. Extraordinary items are defined as both unusual in nature and infrequent in occurrence. Under previous guidance, a reporting entity was required to separately present and disclose extraordinary items. This ASU eliminates from current U.S. GAAP the concept of extraordinary items. However, the ASU retains the presentation and disclosure guidance for items that are unusual in nature or occur infrequently. Items that meet either or both of these criteria must be presented as a separate component on the face of the income statement or, alternatively, disclosed in the notes to the financial statements. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply this ASU either prospectively or retrospectively to all prior periods presented in the financial statements. Early adoption is permitted provided that the ASU is applied from the beginning of the fiscal year of adoption. Ambac has not determined whether it will early adopt this ASU, however adoption of this ASU is not expected to have a material effect on Ambac’s financial statements.

In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis. This ASU makes changes to the VIE model and voting interest ("VOE") model consolidation guidance. The main provisions of the ASU include the following: i) adding a requirement that limited partnerships and similar legal entities must provide partners with either substantive kick-out rights or substantive participating rights over the general partner to qualify as a VOE rather than a VIE; ii) eliminating the presumption that the general partner should consolidate a limited partnership; iii) eliminating certain conditions that need to be met when evaluating whether fees paid to a decision maker or service provider are considered a variable interest; iv) excluding certain fees paid to decision makers or service providers when evaluating which party is the primary beneficiary of a VIE; and v) revising how related parties are evaluated under the VIE guidance. Lastly, the ASU eliminates the indefinite deferral of FAS 167, which allowed reporting entities with interests in certain investment funds to follow previous guidance in FIN 46 (R). However, the ASU permanently exempts reporting entities from consolidating registered money market funds that operate in accordance with Rule 2a-7 of the Investment Company Act of 1940. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Entities may apply this ASU either using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning period of adoption or retrospectively to all prior periods presented in the financial statements. Early adoption is also permitted provided that the ASU is applied from the beginning of the fiscal year of adoption. Ambac will adopt ASU 2015-02 on January 1, 2016 and is currently evaluating the impact of this ASU on its financial statements.